Liquid crystal molecules have been widely used as photomodulation materials due to characteristics such as a self-assembly property, modulation of electrical and optical properties by an external stimulation, and are materials with functionality essential for developing organic light-related materials in the future. Since the liquid crystal molecules basically have a long range order, the liquid crystal molecules aligned on a physically and chemically surface-treated substrate have an alignment effect maintained up to relatively distant molecules. A liquid crystal structure formed by a self-assembly phenomenon to which the long range order of the liquid crystal molecules contributes, has a large birefringence with regard to light, and is able to be modulated and controlled through a relatively easy method by applying external force such as an electric field, a magnetic field, friction force, etc., which is widely used as an optical material.
It was found through x-ray scattering experiment and freeze-fracture TEM experiment (Science 301, 1204 (2003)) that ferroelectric liquid crystal molecules having luminescence properties have a layered structure spontaneously formed in a nano level, the layered structure forms a bundle of microfilaments, and crowd growth thereof forms significantly various optical organizations. In addition, the ferroelectric liquid crystal molecules have a fluorescence property in a visible light region due to four benzene groups present in the molecule, which is applicable as an optical device having high performance with only a single molecule.
For practical application as the optical materials, a single optical organization needs to be expressed, and uniaxial orientation and modulation thereof are required to be generated. However, the existing method for controlling liquid crystal orientation is not able to control a growth direction of the ferroelectric liquid crystal molecules having luminescence properties, and thus, various forms of optical organizations and alignments are not able to be achieved. Accordingly, there is difficulty in using the ferroelectric liquid crystal molecule as the optical material.
The existing related arts, Korean Patent No. 10-1176654 suggests a method of adding the fluorescence property through a process with a different form of organic liquid-crystal molecules in order to use the ferroelectric liquid crystal molecules for an optical device, and Korean Patent No. 10-1174749 describes a method of mixing dye with a liquid crystal compound and a method of forming a polymer film including a dichroic light-absorbing guest by polymerizing the liquid crystal molecules in order to impart a color developing property to the liquid crystal layer forming the optical device. However, those techniques are the method of mixing the liquid crystal molecules or the dye, or the method of polymerizing the liquid crystal molecules for the orientation and the luminescence properties of the liquid crystal molecules, which have a problem in that intrinsic characteristics of the liquid crystal are inhibited by the dye which is a light-emitting material, or production processes such as a polymerization reaction of the organic liquid crystal molecules need to be added.
Therefore, the present inventors made an effort to develop a method of using the photoluminescent ferroelectric liquid crystal molecules for the liquid crystal display, and as a result, found that when a droplet of the ferroelectric liquid crystal molecules was formed on a substrate modified to be molecular phobic, and an electric field in a horizontal direction was applied, a polarizing light-emitting film in which the ferroelectric liquid crystal molecules are uniaxially oriented was able to be produced, and further, when the produced polarizing light-emitting film was used, the liquid crystal display was capable of being implemented even without one polarizing plate and color filter, and completed the present invention.